prime.scm

(define (divides? a b)
    (= (remainder b a) 0)
)

(define (next n)
    (if (= n 2) 3 (+ n 2))
)

(define (find-divisor n test-divisor)
    (cond ((> (square test-divisor) n) n)
          ((divides? test-divisor n) test-divisor)
          (else (find-divisor n (next test-divisor)))
    )
)

(define (smallest-divisor n)
    (find-divisor n 2)
)

(define (prime? n)
    (= n (smallest-divisor n))
)